The present inventor has proposed in PCT patent application PCT/AU86/00321 that the removal of prosthetic cement from the medullary canal of a patient's long bone can be facilitated during a joint prosthesis replacement operation by making two or more longitudinally extending cuts through the bone cement after removal of the old prosthesis. These cuts divide the originally tubular bone cement into a number of segments which may be conveniently levered away from the associated bone and removed from the medullary canal. In the aforementioned patent application means were described for forming such cuts through the prosthetic cement substantially without cutting into the underlying bone. These means included guide means to guide a saw blade along the line of intersection of a longitudinal plane extending through the bone, the prosthetic cement and a prosthetic cavity therein and a bone/prosthetic cement interface intersected by the plane.